Internal combustion tool



April 9, 1935.

J. A. MOULD INTERNAL COMBUSTION TOOL Filed July 11, 1931 INVENTOR MMUMMQA'ITORNEYS 5 UNITED STATES PATENT OFFICE INTERNAL COMBUSTION TOOL JamesA. Mould, Milwaukee, Wis., assigner to Gas Tool Patents Corporation,Chicago, lll., a corporation of Delaware 1 Application July 11, 1931,serial No. 550,180

5 Claims.

'I'his invention relates to improvements in internal combustion tools.The present application is a companion to applications led July 11, 1931by me, respectively bearing Serial Numbers 550,188 and 550,187and-entitled respectively Internal combustion hammers and Internalcombustion engines. 'This application is also a con-- tinuation in partof my application Serial No. 227,656. n1ed October 21, 1927 and entitledInternal combustion hammers.

Internal combustion hammers as previously constructed have been subjectto rather frequent y breakage ofthe compression spring which supportsthe piston andimpels it during the compression stroke. Ordinarily, suchbreakage is overcome by reducing the temper of the spring, but in a toolof this character the power and effectiveness of the tool were found tobe materially decreased by reduction in spring temper to the point thatthe tool became virtually inoperative without overcoming the problems ofbreakage. Experiments with various styles, types and sizes of springshave disclosed the fact that no spring known to spring manufacturers wascapable of withstanding the successive vibratory shocks of the toolwithout crystallization while at the same time maintaining an operativespring load for the proper actuation of the piston. One. of the mostimportant features of the present invention consists in the provision ofa spring assembly by vmeans of which crystallization and breakage may beavoided in a spring subject to compression under the conditions of heatand shock existing in an internal combustion tool of this type.

It has further been found that the gauge and temper of the spring wireemployed in the tool are critical. It hastaken years of experimentationto ascertain and reconcile the various factors involved in this problemand to provide an internal combustion tool with springs which willfunction satisfactorily over long periods of time and without breakage.

In the drawing:

Figure 1 is a vertical axial section through a device embodying thisinvention.

Figure 2 is a view in elevation illustrating in separated positions thecomponent parts of the composite spring used in accordance with thisinvention.

Like parts are identified by the same reference characters throughoutthe several views.

In the particular device illustrated, the cylinder 3 has a jacket 4provided with ns at 5 for heat radiation. The cylinder has an integralhead shouldered at 6 to limit the upward movement of the piston 1. Abovethelimit of piston movement is a spark plug 8 for igniting the charge.

The piston 1 carries a hammer 9 arranged to impact an anvil I0 guidedfor limited axial reciprocation in a bottom closure member II connectedwith the cylinder. Through the closure member II is applied a tool guideI2 adapted to receive any desired tool such as the drill shank I3 whichextends into the socket I4 in anvil I Il to receive impact therefrom.

The sub-piston compression space includes th lower end of cylinder 3 andthe upper end of closure member II into which leads charge admissionport I5 from the charge forming device I I-more fully described in thecompanion applications above referred to. Transfer of the charge fromthe sub-piston compression space to the combustion chamber is effectedunder the control of piston 1 through passages |60 in the piston itself,and a cavity I1 in the wall of the cylinder. The device operates on thetwo cycle principle, the burned gases escaping through exhaust manifoldI8 in the extreme lower position of the piston.

Ignition is controlled directly from the side of piston skirt andco-acting with a cam follower 20 carrying a timer contact 2| which movesto and from engagement with a spring mounted relatively xed timercontact 22.

`Since no crank shaft is employed, it is necessary to provide for springreturn of the piston on its compression stroke. The present inventionrelates particularly-to the means for thus effecting piston return.

The piston spring'proper is shown at 25. It is a low pitch spring,preferably a gauge No. 7 W. 8: M. The gauge is rather critical andshould be confined between W. & M. gauges 5 and 9 inclusive Anythingbeyond this range of sizes has been found inadequate of the device.

The temper of spring 25 is very critical. Long experience of springmanufacturers has Rockwell C Scleroscope scale degree average of Brinellcone kilomodels C and D numbers gram load scleroscopes As above noted,the ordinary remedy for spring breakage is to reduce the temper. In thisparticular instance, however, it has been found that the onlysatisfactory tempers for'the piston spring 25 are those ranging fromRockwell 46 to Rockwell 52 with a decided preference for tempers betweenRockwell 48 and 50. A spring of-No. 7 W. & M. gauge and Rockwell 48 to50 temper, 8% inches long and of the low pitch indicated in the drawingwill, in the first few hours of use, take a permarient set atapproximately 811g inches under an initial load, during use, ofapproximately 35 lbs. and an extreme load of approximately 117 lbs.After this initial set the spring will operate the piston over longperiods of time without injury, breakage, or furtherchange of form.

In practice, the piston spring 25 is preferably supported on, a muchheavier spring 26 which maintains the spring loading of spring. 25 andfunctions irf;l an important manner to absorb /shocks to which theapparatus is subject in operation and which might otherwise crystallizethe piston spring 25. The gauge and temper of the supporting and shockabsorbing spring 26 is not critical. It has been found satisfactory touse No. 4 W. & M. gauge and the customary 42 to 44 Rockwell hardnesstemper. The length of this spring in practice is l-- inches before it issubjected to pressure in the device.

It will be noted that the piston spring is guided about the hammer 9while the supporting spring. 26 is guided about a boss on the upper endof anvil I0. In order to eliminate the necessity of any intermediatespring seat, and to prevent the coils of the two springs frominterwinding, I prefer to wind the springs in opposite directions.

A supporting spring 26 maintains the piston normally at the top of thecylinder. The device is set in motion by supplying its timer withignition current and its sub-piston compression space with a combustiblecharge, and by thus displacing the piston downwardly by means of theplunger mounted in the top of the cylinder. In the downward movement ofthe piston the piston spring 25 is compressed, and when the plunger issharply released the piston is spring pressed t'oward its originalposition to compress the charge in the combustion chamber and controlthe operation of the timer for ignition.

Upon ignition of the charge in the combustion chamber, its suddenexpansion drives the piston down by fluid pressure, thereby compressinga fresh charge for delivery to the combustion chamber and alsosubjecting spring 25 to pressure until its several coils are insubstantial contact. At approximately this time the hammer carried bythe piston will strike the anvil with a sharp percussion which wouldrapidly crystallize the piston spring but for the fact that said springis supported resiliently on spring 26. Since the entirefspring system isunder pressure in all piston positions, spring 26 will tend to expandsulficiently to take up any loss in the length of the spring systemwhich may be occasionedby the shrinkage or set of spring 25.

I claim: 1. In an internal combustion tool, the combination with acylinder, means for introducing and igniting a charge therein, a pistonreciprocable in the cylinder, a hammer carried by the piston, and ananvil in the path of the hammer, of a spring system acting on the pistonin a direction to return it from the anvil, said system includingrelatively longer and shorter springs, the longer spring having a temperof Rockwell 46 to 52 inclusive and a gauge ofI W. & M. 5 to 9 inclusive,and the shorter spring having `a lower temper and a larger gauge thanthe longer spring.

2. In an internal combustion tool, the combination with a cylinder,means for introducing and' igniting a charge therein, apistonreciprocable in the cylinder, a hammer carried by the piston, and ananvil in the path of the hammer, of a piston return spring subject topercussion shock upon engagement of the hammer with the anvil andprovided with a resilient mounting, said piston spring comprising arelatively long spring having a temper in excess of Rockwell hardness 46and a gauge less than 5, and said mounting comprising a relativelyshorter spring of heavier gauge and lower temper.

y 3. The combination with a heavy part movable to and from engagementwith a stop whereby to be subject to percussion, of a spring. sustainingthe load of said part and urging said part from said stop, means forintermittently applying abruptly to said part a pressure wholly inexcess of that of said spring and opposed thereto, whereby invariably tocause the-sharp striking of said stop by said part, and a yieldablemounting for said spring interposed between said stop and spring, saidmounting being yieldable only to pressures of surge and impact in excessof those required for the support of said part, whereby to cushion saidspring from the crystallizing effect of impact of said part upon saidstop.

4. In a device of the character described, the combination' with acylinder, a piston, a hammer connected with said piston and an anvil, ofa compression spring acting upon said hammer and piston in opposition tothe movement thereof toward said anvil, said spring being of adequatestrength to store a portion of the energy developed in such movement,and a secondary spring adapted to act through the first in opposition tosuch movement and so constructed as to be stronger than said firstmentioned spring, whereby to provide a resilient mounting adapted toabsorb shock resulting from the'blow of said hammer on said anvil.

5. In a device of the character described, the

combination with a cylinder, a reciprocable piston therein, a hammerconnected with said piston and an anvil in the path of said hammer, ofspring means conned between said anvil and piston and comprising arelatively long spring of adequate strength to receive a portion of theenergy developed by piston movement toward said anvil and to return saidpiston from said anvil,

series therewith between said piston and said anvil, whereby to beadapted to absorb shock to said first mentioned spring, said springbeing oppositely wound whereby each provides a seattor the other. 1JAMES A. MOULD.

